Deposition of diffusion barrier

Abstract

The invention provides a stacked wafer structure with decreased failures. In one embodiment, there is a barrier layer deposited on exposed surfaces of conductors that extend across a distance between first and second device structures. The barrier layer may prevent diffusion and electromigration of the conductor material, which may decrease incidences of shorts and voids in the stacked wafer structure.

1. A method, comprising:
 forming a first device structure with patterned conductors; 
 depositing a barrier layer on exposed surfaces of the patterned conductors wherein depositing a barrier layer comprises exposing the exposed surfaces of the patterned conductors to a solution; 
 bonding the first device structure to a second device structure; 
 wherein the first device structure is bonded to the second device structure prior to depositing the barrier layer on exposed portions of the patterned conductors; and 
 wherein the solution comprises cobalt ions and the barrier layer comprises cobalt. 
 
     
     
       2. The method of  claim 1 , wherein exposing the exposed portions of the patterned conductors to a solution comprises dipping the first device structure at least partially into the solution. 
     
     
       3. The method of  claim 1 , wherein exposing the exposed portions of the patterned conductors to a solution comprises applying solution with a syringe. 
     
     
       4. The method of  claim 1 , wherein exposing the exposed portions of the patterned conductors to a solution comprises flowing the solution to the conductors in aerosol form carried by supercritical CO 2 . 
     
     
       5. The method of  claim 1 , further comprising removing excess solution. 
     
     
       6. The method of  claim 1 , wherein the patterned conductors are copper and the barrier layer is selectively deposited on the conductors by electroless deposition. 
     
     
       7. A method comprising:
 forming a first device structure with conductors extending beyond a surface of the first device structure, wherein the conductors comprise copper; 
 forming a second device structure; 
 bonding the first device structure to the second device structure so that the conductors have exposed surfaces in a gap between the first device structure and the second device structure; and 
 forming a barrier layer on substantially all the exposed surfaces of the conductors after bonding the first device structure to the second device structure, wherein forming the barrier layer comprises exposing the exposed surfaces of the conductors to a solution to form the barrier layer and wherein the solution comprises cobalt ions and the barrier layer comprises cobalt. 
 
     
     
       8. The method of  claim 7 , wherein the barrier layer is formed by selectively depositing the barrier layer on the conductors by electroless deposition.